[PATCH 1/4] target/i386/mshv: fix vCPU run result contract

[Magnus Kulke]

Currently the return semantics of mshv_run_vcpu() are broken. They
return a mix of int and exit_reason, ignoring the out param *exit.

This change propagates errno's to the call site and sets the *exit value
accordingly. We also consider the case when an ioctl has return due to a
qemu-requested interruption of the call, this is a legitimate condition
that should not produce an error.

Fixes: 6dec60528c4 (target/i386/mshv: Implement mshv_vcpu_run())
Signed-off-by: Magnus Kulke <magnusku...@linux.microsoft.com>
---
 target/i386/mshv/mshv-cpu.c | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/target/i386/mshv/mshv-cpu.c b/target/i386/mshv/mshv-cpu.c
index 4df73bb497..e3c155da2e 100644
--- a/target/i386/mshv/mshv-cpu.c
+++ b/target/i386/mshv/mshv-cpu.c
@@ -2124,7 +2124,6 @@ static int arch_set_single_step(CPUState *cpu, bool 
enable)
 int mshv_run_vcpu(int vm_fd, CPUState *cpu, hv_message *msg, MshvVmExit *exit)
 {
     int ret;
-    enum MshvVmExit exit_reason;
     int cpu_fd = mshv_vcpufd(cpu);
     bool single_step;
 
@@ -2142,7 +2141,12 @@ int mshv_run_vcpu(int vm_fd, CPUState *cpu, hv_message 
*msg, MshvVmExit *exit)
 
     ret = ioctl(cpu_fd, MSHV_RUN_VP, msg);
     if (ret < 0) {
-        return MshvVmExitShutdown;
+        if (errno == EINTR) {
+            *exit = MshvVmExitSpecial;
+            return 0;
+        }
+        error_report("failed to run vCPU: %s", strerror(errno));
+        return -errno;
     }
 
     /* disable single stepping by flipping RFLAGS.TF */
@@ -2154,31 +2158,33 @@ int mshv_run_vcpu(int vm_fd, CPUState *cpu, hv_message 
*msg, MshvVmExit *exit)
 
     switch (msg->header.message_type) {
     case HVMSG_UNRECOVERABLE_EXCEPTION:
-        return MshvVmExitShutdown;
+        *exit = MshvVmExitShutdown;
+        return 0;
     case HVMSG_UNMAPPED_GPA:
     case HVMSG_GPA_INTERCEPT:
-        ret = handle_mmio(cpu, msg, &exit_reason);
+        ret = handle_mmio(cpu, msg, exit);
         if (ret < 0) {
             error_report("failed to handle mmio");
-            return -1;
+            return ret;
         }
-        return exit_reason;
+        return 0;
     case HVMSG_X64_IO_PORT_INTERCEPT:
         ret = handle_pio(cpu, msg);
         if (ret < 0) {
-            return MshvVmExitSpecial;
+            error_report("failed to handle PIO");
+            return ret;
         }
-        return MshvVmExitIgnore;
+        *exit = MshvVmExitIgnore;
+        return 0;
     case HVMSG_X64_EXCEPTION_INTERCEPT:
         bql_lock();
-        ret = handle_exception_interrupt(cpu, msg, &exit_reason);
+        ret = handle_exception_interrupt(cpu, msg, exit);
         bql_unlock();
         if (ret < 0) {
             error_report("failed to handle exception intercept");
             return -1;
         }
-        *exit = exit_reason;
-        return exit_reason;
+        return 0;
     default:
         break;
     }
-- 
2.34.1